Low pressure vapour of polar fluid condenser based on liquefaction in running non-polar liquid

ABSTRACT

The present disclosure provides a method of collecting, including condensing, vapour of a polar fluid inside a liquid that is subjected to continuous flow in a process system, the liquid having a low vapour pressure (i.e. non-volatile) and being a non-polar liquid. The collection of the vapour, by condensation, occurs via four transition steps: (1) vapour (e.g. vapour of water) transferring sensible heat to the liquid (e.g. oil), (2) bubbles containing vapour collapse and become water in hot oil, (3) dissolved vapour liquefies through heat removal at elevated temperatures, and (4) oil and water are separated due to the difference in polarity between the polar fluid and the non-volatile non-polar liquid. The present method converts low grade (i.e. low temperature) waste heat into high grade heat source suitable for efficient heat rejection or heat recovery applications. An apparatus for collecting vapour of a polar fluid in a non-volatile non-polar liquid is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Singapore Patent Application No. 10201702478Q, filed 27 Mar. 2017, the content of it being hereby incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

The present disclosure relates to a method of collecting vapour of a polar fluid in a non-volatile non-polar liquid. The present disclosure also relates to an apparatus for collecting vapour of a polar fluid in a non-volatile non-polar liquid.

BACKGROUND

Liquefaction is a phase change process that converts a solid or gaseous substance into liquid. A type of liquefaction is condensation. Condensation converts a substance in its gas phase into its liquid phase. Typically, a condenser is used for condensation. A condenser is a device that provides the capacity for heat rejection to the environment. This means that the gaseous substance loses heat energy, through the condenser, to the environment to become a liquid. From the perspective of a phase diagram, this means that the phase of the substance starts from a point to the right of the saturated curve (vapour state) and moves to a point left of the saturated curve (liquid phase), as illustrated in FIG. 1.

In some applications, the vapour may reach a condenser in its super-heated state, i.e. a state represented by a point to the right of the saturated curve. At super-heated state, the vapour may behave like an ideal gas, exhibiting a property where there is linear dependence between pressure and temperature. The intersection point of the super-heated lines (represented by the broken lines in FIG. 1) and the saturated curve determines the maximum limit for the heat sink temperature of the environment (T_(env)) that a condenser can use, i.e. the highest temperature of the environment for a condenser to transfer heat out.

For condensation to occur, a saturated state (a point on the saturated curve of FIG. 1) needs to be attained. This, however, may not be sufficient because the molecules have to be close enough for their bonds, e.g. hydrogen bonds, to interact, and latent heat released through recombination of molecules have to be transferred away for the liquid phase to form.

Heat rejected in a condenser may include (i) sensible heat of super-heated vapour and (ii) latent heat released through phase transition. The sensible heat from super-heated vapour is proportional to the temperature difference between the vapour temperature and the temperature of the point where the super-heated vapour line intersects the saturated curve (see FIG. 1). Bearing these in mind, before a super-heated low pressure vapour condenses, it has to reject a larger amount of heat than a super-heated high pressure vapour, if both were at the same initial temperature (see FIG. 1). The rate of heat rejection is also proportional to the temperature difference. Nevertheless, a low pressure vapour is still condensable, albeit the condensation may be limited by a low probability of molecules' interaction due to its low pressure, and this becomes the dominant factor for condensation. In other words, the overall heat transfer is dominated by (ii), i.e. the latent heat component, while removal of sensible heat component (i) may account for less than 10% of the cooling process. Latent heat is typically rejected at constant temperature and proportional to latent heat of vapourization. At lower pressures, the value for the latent heat of vapourization is higher, making it harder for low pressure vapours to condense. In addition to component (ii), heat transfer across the condenser wall should match the latent heat released from condensation.

For low pressure vapours, their rate of heat transfer tends to be slower due to lower remaining temperature difference between the saturation point and T_(env) (see FIG. 1) and this part often dominates the overall heat transfer capacity. That is why condensation of low pressure vapours, accordingly, tends to be less efficient than high pressure vapours and requires much larger and more expensive condensers.

Bearing in mind the difference in condensation for high and low pressure vapours, condensers may be categorized into passive and active condensers.

Performance of a passive condenser is determined by the temperature of the environment to which heat is rejected. This temperature (T_(env)) has to be less than the intersection point, as mentioned above and as illustrated in FIG. 1. Even for super-heated low pressure vapours, it can be used as long as this temperature requirement is fulfilled.

Alternatively, for the cases where T_(env) is larger than the intersection point (FIG. 2), an active condenser may be used. There are several types of active condensers, which may differ in terms of how they operate, for example, (i) by cold traps, (ii) by vapour compression, (iii) vapour absorption and desorption (absorption-desorption), or (iv) jet ejectors.

Cold traps are straightforward but are generally least economical. In cold traps, the cooling fluid is first pre-cooled in a separate system to a temperature well below the intersection point. This means considerable amount of heat needs to be rejected to the environment in an auxiliary system in advance and cold trap is just using this “credit” (see FIG. 2, solid arrow 2).

For vapour compression or absorption-desorption active condensers, the idea for both are the same. Low pressure vapours are converted to high pressure vapours so that condensation can occur more easily (see broken arrow 1 of FIG. 2). Their conversion mechanisms, however, differ. In a compressor, the vapour is mechanically compressed, resulting in an increase of the vapour's pressure and temperature. In absorption/desorption, the low pressure vapours are first absorbed in a liquid solution (e.g. LiBr) to give rise to a saturated liquid. The saturated liquid may then be pumped out of the low pressure chamber into a higher pressure chamber. An external heat source is then used to desorp vapour from the saturated liquid. The result is that the same vapour is released in a super-heated high pressure condition, allowing the vapour to be more readily condensed.

For jet ejectors, a low pressure vapour is converted to a high pressure vapour by relying on a fluid moving at much higher pressures. In this way, a high pressure vapour can be condensed instead, albeit a considerably larger volume.

Despite the above, such condensers have their limitations, for example, when vacuum evaporation and/or boiling is applied. In vacuum boiling, the bulk water is separated into a cold liquid phase and a hot vapour phase. If the vapour is not efficiently removed from the chamber, vacuum is lost and the cooling process may seize. This typically occurs since the vacuum pump may not be able to handle large volumes of vapour. That is one vital reason why the vapour should be condensed before it reaches the vacuum pump.

A limitation with cold traps is that the generation of sub-cooled fluid, or even solid, requires a separate chilling station and makes the whole process inefficient.

Compressors tend to be inefficient due to the large volume of vapour that they compress, which consumes high power.

A limitation also exists with absorption/desorption condensers as they require an external heat source, which is often a bulky system, may not be available and/or require to be constructed. Additionally, the used chemicals may generate acids at elevated water absorption levels, which may rapidly degrade the system.

A limitation for jet ejecters is that they require large quantities of high pressure vapour to operate and also large quantities of cooling water for condensation of that high pressure vapour.

There is thus a need to provide for a solution that ameliorates and/or resolves one or more of the issues and/or limitations mentioned above.

SUMMARY

In one aspect, there is provided for a method of collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising:

providing in an enclosed container an initial volume of the non-volatile non-polar liquid;

maintaining a reduced pressure above the surface of the non-volatile non-polar liquid;

introducing a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid;

introducing a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid; and

withdrawing an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid.

In another aspect, there is provided for an apparatus for collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising:

an enclosed container comprising an initial volume of the non-volatile non-polar liquid;

a first outlet connected to a pump which reduces pressure above the surface of the non-volatile non-polar liquid;

a first inlet configured to introduce a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid;

a second inlet configured to introduce a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid; and

a second outlet configured to withdraw an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present disclosure are described with reference to the following drawings, in which:

FIG. 1 shows a typical phase diagram for super-heated high pressure and super-heated low pressure vapours. Specifically, FIG. 1 shows the effect of temperature on a super-heated high pressure vapour (top arrow) and a super-heated low pressure vapour (bottom arrow).

FIG. 2 shows a phase diagram for active condensers where T_(env) is more than the intersection point for a super-heated low pressure vapour. Process 1 (broken arrow 1) represents either vapour compression or absorption-desorption. Process 2 (solid arrow 2) represents the use of cold traps.

FIG. 3 shows an apparatus that serves as a low pressure vapour condenser, based on liquefaction in a continuous system of mineral oil, according to one embodiment disclosed herein.

FIG. 4 shows a phase diagram for the phase changes that occur in the present method and apparatus. Process 1 (broken arrow 1) represents the phase change process for either vapour compression or absorption-desorption. Specifically, process 2 (solid arrow 2) represents the phase change process that occurs when a cold trap is used. Process 3 (dotted arrow 3) represents the phase change for a low pressure vapour condenser based on liquefaction in a continuous system of mineral oil, i.e. present method and apparatus.

FIG. 5 shows a process diagram for a system that includes the present apparatus. The present apparatus operates based on the present method, where both the present apparatus and method are described in at least one of the embodiments disclosed herein.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced.

Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

The present disclosure relates to a method of collecting vapour of a polar fluid in a non-volatile non-polar liquid and an apparatus for collecting such a vapour in the non-volatile non-polar liquid. The collection of the vapour includes condensation of the vapour in the non-volatile non-polar liquid.

The present method and apparatus circumvent the limitations as described above. The present method and apparatus also prevent condensable vapour of the polar fluid, e.g. water, from entering into a vacuum system, such as a vacuum pump, which can condense within a compression chamber of the vacuum pump and reduce the vacuum efficiency or even shut down the vacuum system. The present method and apparatus further generate cooled polar fluid, which can be used as a coolant. The present method and apparatus capitalize on the following circumstance.

Bubbles in boiling liquid, e.g. water, contain super-heated vapour. The super-heated vapour may be a vapour of a polar fluid. Only the highest energy molecules, according to Maxwell-Boltzmann distribution, can form the bubbles. If these molecules are separated from the rest of the liquid, they may be taken as a very hot gas. Advantageously, heat transfer from the bubbles moving in a sub-cooled liquid is highly efficient and can reach more than 10 kW/m² due to volumetric heat loss and convective heat transfer.

The definitions of certain terms are first discussed before going into details of the various embodiments of the present method and apparatus.

The term “fluid” as used herein is a general term covering liquids and gases. The gases include vapours.

The term “polar” as used herein refers to a molecule having a positive charge at one end and a negative charge at the other end. For instance, a polar fluid refers to a fluid comprised of molecules having such positive and negative charges positioned as defined. A non-limiting example of a polar fluid may be water. Meanwhile, the term “non-polar” as used herein refers to a molecule that does not have charge redistribution and the ends of the molecules are neutral. For instance, a non-polar liquid refers to a liquid comprised of molecules having no charge redistribution and the ends of each of the molecules are neutral. A non-limiting example of a non-polar liquid may be a mineral oil.

The term “non-volatile” as used herein refers to liquid that does not readily evaporate. This includes liquids that do not readily evaporate under vacuum or partial vacuum, where pressures are below atmospheric pressure. For example, a mineral oil that does not vapourize at 3 kPa can be referred to as a non-volatile liquid in the context of the present disclosure.

The term “immiscible” as used herein refers to liquids that remain separated even when they are mixed. For example, oil and water remain as separate liquids even when mixed. That is to say, neither oil nor water disappears into each other after mixing. Notwithstanding this, the term “dissolved” as used in the context of the present disclosure means that individual molecules of one substance may exist in another substance without agglomerating into clusters or droplets and without breakdown of the molecules. As a general example, when vapour of a volatile fluid is dissolved in a non-volatile liquid, it means that the vapour molecules may exist in the non-volatile liquid. In a further example, when it is described that oil contains dissolved water, it means that individual molecules of water may exist in oil. This is to be distinguished from the context where sodium chloride dissolves in water, in which the sodium chloride breaks down into its ions.

The term “super-heated” as used herein refers to any vapour with a pressure and temperature combination that places it on the right of the saturation curve in its phase diagram.

The term “phase” as used herein refers to the physical state of a material, e.g. solid, liquid or vapour.

The word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the invention.

In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance.

As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

Unless specified otherwise, the terms “comprising” and “comprise”, and grammatical variants thereof, are intended to represent “open” or “inclusive” language such that they include recited elements but also permit inclusion of additional, unrecited elements.

Details of the various embodiments are now described below.

In the present disclosure, there is provided for a method of collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising: providing in an enclosed container an initial volume of the non-volatile non-polar liquid, maintaining a reduced pressure above the surface of the non-volatile non-polar liquid, introducing a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid, introducing a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid, and withdrawing an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid.

In the present disclosure, there is provided for a method of collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising: providing in an enclosed container an initial volume of the polar fluid and an initial volume of the non-volatile non-polar liquid, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid, maintaining a reduced pressure above the surface of the non-volatile non-polar liquid, introducing a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, introducing a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid, and withdrawing an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid. The polar fluid may be a polar liquid in various embodiments. In some embodiments, the present method may start without the initial volume of the polar fluid. That is to say, the present method may start with just the initial volume of the non-volatile non-polar liquid while the polar fluid may then accumulate at the bottom of the enclosed container, away from the initial volume of the non-volatile non-polar liquid, when the process starts.

The collection of such vapour may include condensing the vapour in the non-volatile non-polar liquid.

In various embodiments, maintaining the reduced pressure may comprise of removing non-condensable gases (e.g. air) such that the pressure (at least the pressure above the surface of the non-volatile non-polar liquid in the enclosed container) goes down to a partial pressure that is below a value corresponding to the boiling temperature of the polar fluid at the required temperature set-point. This set-point refers to the condition where at least some of the polar fluid may be converted into its vapour form. In other words, the reduced pressure may be set at a pressure which is sufficiently low to convert at least some of the polar fluid into the vapour of the polar fluid.

In various embodiments, the pressure may be reduced to a level sufficient to cause boiling in the polar fluid at a required temperature range. The required temperature range may depend on the type of polar fluid, the type of non-volatile non-polar liquid, and/or the conditions of the system in which the present method is utilized. In various embodiments, the pressure may be 3 kPa or less. This depends on, for example, the polar fluid and the non-volatile non-polar liquid used.

In various embodiments, the polar fluid may comprise or may be, for example, water. In various embodiments, the polar liquid may comprise or may be, for example, water. The polar fluid may be any polar fluid that is denser than the non-volatile non-polar liquid.

In various embodiments, the non-volatile non-polar liquid may comprise or may be, for example, hydrocarbon, non-synthetic lubricant, mineral oil and/or vegetable oil. The non-volatile non-polar liquid may be any non-volatile non-polar liquid that has a density lower than the polar liquid or polar fluid. The non-volatile non-polar liquid is immiscible and does not react with the polar fluid. Other suitable non-volatile non-polar liquid that is immiscible and does not react with the polar fluid may be used. In a non-limiting example, the non-volatile non-polar liquid may be mineral oil while the polar fluid may be water. In such an example, the vapour of the polar fluid to be condensed may be water vapour and the polar fluid then collected is water. Advantageously, the polar fluid and non-volatile non-polar liquid allow for a distinguishable separation of both even when they are in contact with each other.

In various embodiments, the vapour of the polar fluid (e.g. polar liquid) may comprise or consist of, for example, water vapour. Other vapours of other polar liquids may also be worked on by the present method provided that it is, apart from density difference, immiscible with the non-volatile non-polar liquid. Since the vapour of the polar fluid may be water vapour and the polar fluid may be water, this means that the polar liquid and the vapour are of the same substance. The vapour of the polar fluid may exist as bubbles, for example, in the polar fluid and/or in the non-volatile non-polar liquid.

In various embodiments of the present method, introducing the second input to stream may comprise or consist of delivering the non-volatile non-polar liquid from a position which is at a same height as or above the first input stream. As the second input stream of non-volatile non-polar liquid is used to collect or condense the vapour, the configuration of introducing the non-volatile non-polar liquid at a position which is at a same height as or above the first input stream advantageously allows for and/or maximizes, the heat exchange and/or the distance over which heat transfer occurs, between the hot vapour bubbles of the polar liquid and the non-volatile non-polar liquid, thereby helping to condense and collect more vapour. The first input stream may be introduced into the section containing the polar fluid or the non-volatile non-polar liquid.

In some embodiments, the method may comprise introducing the second input stream into the section of the enclosed container containing the non-volatile non-polar liquid, which is disposed above the section containing the polar fluid, as the non-volatile non-polar liquid is less dense than the polar fluid. This advantageously prevents the escape of any vapour from the section containing the polar fluid into the vacuum system that maintains the reduced pressure.

In various embodiments, introducing the second input stream may comprise delivering the non-volatile non-polar liquid with some polar fluid present in the non-volatile non-polar liquid. The some polar fluid (e.g. water) may be present as free water (liquid water), as an emulsion (e.g. oil-water emulsion when the non-volatile non-polar liquid is oil), and/or in a dissolved form (e.g. individual molecules of water in oil when the non-volatile non-polar liquid is oil). The some polar fluid may be, as a non-limiting example, present in less than 100 ppm of the non-volatile non-polar liquid that is delivered. In some instances, there may be no polar fluid present in the non-volatile non-polar liquid that is delivered in the second input stream. Advantageously, using a non-volatile non-polar liquid that contains less of the polar fluid and/or less of the vapour of the polar fluid in the second input stream, e.g. at the start, enables the non-volatile non-polar liquid to collect and condense more of the vapour. If a non-volatile non-polar liquid that is saturated with dissolved polar fluid is used in the second input stream, e.g. at the start, the amount of collected and condensed vapour may decrease due to less capacity of the non-volatile non-polar liquid to hold the polar fluid or the vapour of the polar fluid.

In various embodiments, the method may further comprise withdrawing the polar fluid or polar liquid from a height which is below the first input stream. Hence, cooled polar liquid, e.g. cooled water, may be withdrawn and channeled to other parts of a system or the present apparatus, to be used as cooling agent (coolant).

In various embodiments, the method may further comprise cooling the mixture to condense the vapour of the polar fluid. This helps to condense more vapour in the mixture that is withdrawn from the section containing the non-volatile non-polar liquid. A heat exchanger or chimney with sufficient air flow for heat exchange may be used for the cooling. The mixture may be mixed with a non-volatile non-polar liquid having substantially low polar fluid content to condense the vapour of the polar fluid according to some embodiments. The vapour of the polar fluid may exist as bubbles.

In the present disclosure, there is also provided an apparatus for collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising: an enclosed container comprising an initial volume of the non-volatile non-polar liquid, a first outlet connected to a pump which reduces pressure above the surface of the non-volatile non-polar liquid, a first inlet configured to introduce a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid, a second inlet configured to introduce a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid, and a second outlet configured to withdraw an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid.

The present disclosure also provides for an apparatus for collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising: an enclosed container comprising an initial volume of the polar fluid and an initial volume of the non-volatile non-polar liquid, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid, a first outlet connected to a pump which reduces pressure above the surface of the non-volatile non-polar liquid, a first inlet configured to introduce a first input stream comprising the polar fluid or a super-heated to vapour of the polar fluid into the enclosed container, a second inlet configured to introduce a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid, and a second outlet configured to withdraw an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid. In some embodiments, the present apparatus may start without the initial volume of the polar fluid. That is to say, the present apparatus may start with just the initial volume of the non-volatile non-polar liquid while the polar fluid may then accumulate at the bottom of the enclosed container, away from the initial volume of the non-volatile non-polar liquid, when the process starts.

Various embodiments of the present method, and advantages associated with various embodiments of the present method, as described above, may be applicable to the present apparatus, and vice versa.

In various embodiments, the pump may be a positive displacement pump. In various embodiments, the pump used to remove oil with vapour from the vacuum chamber may comprise or may be a positive displacement pump. In various embodiments, the pump used to reduce pressure above the surface of the non-volatile non-polar liquid may remove non-condensable gases (e.g. air) such that the pressure (at least the pressure above the surface of the non-volatile non-polar liquid in the enclosed container) goes down to a partial pressure that is below a value corresponding to the boiling temperature of the polar fluid at the required temperature set-point. This set-point refers to the condition where at least some of the polar fluid may be converted into its vapour form. In other words, the reduced pressure may be set at a pressure which is sufficiently low to convert at least some of the polar fluid into the vapour of the polar fluid. In various embodiments, the pump may reduce pressure to a level sufficient to cause boiling in the polar fluid at a required temperature range. The required temperature range may depend on the type of polar fluid, the type of non-volatile non-polar liquid, and/or the conditions of the system in which the present apparatus is utilized. In various embodiments, the pressure may be 3 kPa or less. This depends on, for example, the polar fluid and the non-volatile non-polar liquid used.

In some embodiments, the first inlet may comprise one end disposed at any height in the enclosed container provided that height is lower than the position at which the second inlet introduces the non-volatile non-polar liquid into the enclosed container. This advantageously allows for and/or maximizes, the heat exchange and/or the distance over which heat transfer occurs, between the hot vapour bubbles of the polar liquid and the non-volatile non-polar liquid, thereby helping to condense and collect more of the polar liquid and/or polar vapour. The first inlet may comprise one end disposed in the section containing the polar fluid or the non-volatile non-polar liquid according to some embodiments.

In various embodiments, the second inlet of the apparatus may comprise one end disposed at a position in the section containing the non-volatile non-polar liquid which is at a same height as or above the one end of the first inlet that may be disposed in the section containing the non-volatile non-polar liquid. This helps to introduce the non-volatile non-polar liquid into the apparatus from a position over where the polar liquid is introduced into the enclosed container, which reduces chances of polar fluid of being pumped out from the chamber together with the non-volatile non-polar liquid and vapour of the polar fluid. If too much polar fluid in such a mixture of polar fluid, non-volatile non-polar liquid and vapour of the polar fluid is pumped out in the output stream, efficiency of the system may be reduced.

In various embodiments, the second inlet may be configured to introduce the second input stream comprising the non-volatile non-polar liquid with some polar fluid present in the non-volatile non-polar liquid. The amount of polar fluid present in the non-volatile non-polar liquid that is delivered has been described above. In some instances, there may be no polar fluid present in the non-volatile non-polar liquid that is delivered in the second input stream.

In various embodiments, the apparatus may have the second outlet comprises one end disposed at a position in the section containing the non-volatile non-polar liquid which is at a same height as or above the one end of the first inlet that may be disposed in the section containing the non-volatile non-polar liquid. The second outlet may be at least five times larger, in terms of the cross-section, than the first inlet as bubbles occupy a considerable volume in the fluid that is pumped out. This allows more vapour and vapour bubbles to be withdrawn from the apparatus. The actuation unit in FIG. 5 is for generating a lower pressure than the pressure above the non-volatile non-polar liquid, which ensures that all bubbles are drawn towards the second outlet. This allows more vapour and vapour bubbles to be withdrawn from the apparatus. In an ideal system, when no bubbles escape the interface between the non-volatile non-polar liquid and vacuum, the required vacuum pump then needs very little pumping capacity as its function may then be reduced to removing non-condensable gases (e.g. air) that were either dissolved in the liquids before system initiation or entered the system through leaks.

In various embodiments, the apparatus may contain other outlets. For example, there may be another outlet for withdrawing cooled polar liquid from the enclosed container. Such an outlet may be disposed at a position below and away from the one end of the first inlet that may be disposed in the section containing the polar fluid or the non-volatile non-polar liquid or at a height below the one end of the first inlet that may be disposed in the section containing the polar fluid or the non-volatile non-polar liquid, where the cooled polar fluid can then be routed to be used as a coolant.

In various embodiments, the apparatus may further comprise a heat exchanger which cools the mixture to condense the vapour of the polar fluid. This helps to condense more vapour of the polar fluid in the mixture that is withdrawn from the section containing the non-volatile non-polar liquid. A heat exchanger or chimney with sufficient air flow for heat exchange may be used.

In summary, the present disclosure provides a method of collecting, including condensing, vapour inside a liquid that is subjected to continuous flow in a process system, the liquid having a low vapour pressure (i.e. non-volatile) and being a non-polar liquid. The collection of the vapour, by condensation, occurs via four transition steps, which include (1) vapour (e.g. vapour of water) transferring sensible heat to the liquid (e.g. oil), (2) bubbles containing vapour collapse and become water in hot oil, (3) dissolved vapour liquefies through heat removal at elevated temperatures, and (4) oil and water are separated due to the difference in polarity between the polar fluid and the non-volatile non-polar liquid.

The present method thus converts low grade (i.e. low temperature) waste heat into high grade heat source suitable for efficient heat rejection or heat recovery applications.

Various embodiments of the present method and apparatus, include a chamber for vacuum boiling of a polar liquid (e.g. water), where low density and hot vapour of the polar fluid may be separated from higher density cold polar fluid. This chamber may be the enclosed container. In such embodiments, the hot vapour of the polar fluid travels through a floating layer of non-volatile non-polar liquid (e.g. mineral oil) that has a density lower than the polar fluid (e.g. polar liquid). The vapour of the polar fluid may be collapsed to form water in the oil and withdrawn from the chamber in the form of an oil/water solution together with vapour bubbles that have not collapsed and liquefied hot water.

The present method and apparatus may involve a heat exchanger with hot oil/water solution that is enclosed in a chimney structure that allows for cooling with almost zero energy input. The heat exchanger may be designed to target maximum liquefaction of water in oil at existing ambient temperature. The heat exchanger should be connected to an oil/water separator, for example, to complete the vapour condensation cycle and return purified cold oil into the system and/or apparatus. The oil/water separator may include additional cooling device for further separation of oil and water, and/or elimination of particle debris before recycling both the oil and/or water.

While the methods described above are illustrated and described as a series of steps or events, it will be appreciated that any ordering of such steps or events are not to be interpreted in a limiting sense. For example, some steps may occur in different orders and/or concurrently with other steps or events apart from those illustrated and/or described herein. In addition, not all illustrated steps may be required to implement one or more aspects or embodiments described herein. Also, one or more of the steps depicted herein may be carried out in one or more separate acts and/or phases.

EXAMPLES

The present method and apparatus, as disclosed above, are described in the examples below.

Example 1: The Present Method and Apparatus

The present apparatus was set up as described below, and is illustrated in FIG. 3. The present method was carried out using the present apparatus.

A chamber or reservoir was partly filed with water and a mineral oil that is non-polar and has low vapour pressure. Since the mineral oil has low vapour pressure, it does not readily evaporate and is, therefore, a non-volatile non-polar liquid. Other non-volatile non-polar liquids, and other polar liquids for replacing the water, may be used as long as they are immiscible, e.g. mineral oil and water, respectively, and do not react with each other. The non-volatile non-polar liquid and the polar liquid, for example, mineral oil and water, respectively, should also differ in density. Due to different densities, the mineral oil floats on water.

The space above the oil was evacuated to vacuum below 30 mbar (3 kPa). Such a condition forces high energy molecules in the polar fluid (e.g. a polar liquid of water) to form vapour bubbles that can escape towards the direction of the vacuum due to buoyancy force, which are forced to move through the oil layer. Based on Maxwell-Boltzmann distribution, the escape of the high energy molecules causes a left shift of the distribution in remaining water leading to lower water temperature. Exceptionally high heat removal rates during boiling help to ensure that the temperature of the liquid water stays constant such that the temperature is independent of heat input from the incoming hot water or steam (super-heated water vapour) (FIG. 3). The temperature tends to stay constant at about 25° C. as the vacuum of 30 mbar above the oil surface was maintained, which was achievable even when most of the bubbles were removed by oil pumping.

The hot water inlet was positioned above the oil/water boundary. The incoming hot water separated into water vapour and liquid water. The separation occurs as the water vapour has a density lower than the oil while the liquid water has a density higher than the oil. Accordingly, vapour bubbles with energetic molecules ascend in the oil while cooled polar water descends in the oil.

At the bottom of the chamber, a water drain was introduced or positioned to remove excess water. The removed water may serve as a supply of cold water to the cooling system or for cooling applications.

To illustrate the workings of the present method and apparatus, it was assumed and only for the purpose of illustration, that the whole apparatus rejects 140 kW of heat from the incoming water. Latent heat of the vapour of the polar water at 30 mbar vacuum is 2400 kJ/kg. That means to evaporate water through boiling, only 58 mL/s of incoming water was needed to achieve the above result, which is the collection and condensation of water in oil. If all generated vapour bubbles collapse to form water in the oil (which is held at an incoming oil flowrate of 1 L/s), and with a specific heat capacity of 1.67 kJ/kg K and density of 0.87 kg/L for the oil, and assuming all the heat from the vapour bubbles was absorbed in oil, the oil temperature would then theoretically increase by 96° C. This implies that if oil was introduced at 30° C., it would reach 126° C. and may be withdrawn from the apparatus at 126° C. At slower flowrates, the temperature increases proportionally.

Despite the above, not all bubbles may collapse in oil because every collapse results in the transfer of heat from the bubbles to the oil, causing the oil temperature to increase, which in turn absorbs less heat from bubbles, i.e. heat loss from vapour to oil decreases. Besides that, there is a limit to how much water a mineral oil can hold. At 100° C., oil may only hold 800 ppm or 0.8 g of water per liter of oil. As a result, some bubbles may not collapse and may survive long enough to be withdrawn at the output pipe while some vapour may liquefy into water droplets that descend due to gravity. The speed of descend, however, may be too slow and most of the droplets may therefore get sucked into the oil/water output pipe.

Collapsing of all the bubbles and heat removal from oil may require additional units that will be discussed in example 3 below. Nevertheless, this example demonstrates that the present method and apparatus allow vapour compression/condensation to occur in the oil based on heat transfer without the need for external energy input or work done, apart from oil pumping that only requires a fraction of power.

Example 2: Comparison to Conventional Condensers

The present method may be compared to that of standard active condensers through a phase diagram as shown in FIG. 4.

It is envisaged that the present process is represented by process 3 (the broken arrow 3) in FIG. 4. The collapse of the bubbles is a form of vapour compression. All the latent heat is effectively transferred to the oil and then rejected at elevated temperature.

In comparison with process 1 (broken arrow 1 of FIG. 4) that uses a standard compressor, the present method (broken arrow 3 of FIG. 4) advantageously differs in to that the effective pressure in the bubbles is larger than the pressure in “free vapour” (i.e. vapour not in the form of bubbles) after the bubbles escaped the interface between the non-volatile non-polar liquid and vacuum. To elaborate, processes 1 and 3 may begin with the same vacuum pressure to initiate boiling. For process 1, the vapour reaches the compressor at the same vacuum pressure. If the compressor produces, for example, compressed vapour with a pressure value that is three times higher than the initial vacuum pressure for boiling, the compression ratio may then be taken as 3. In contrast, the vapour of the present method, which exists in the form of bubbles confined in the non-volatile non-polar liquid (e.g. oil), tends to have an internal pressure higher than the initial vacuum pressure for initiating boiling, and this implies that less compression is needed for such vapour bubbles. Hence, a lower compression ratio is required. The ratio between the final and initial pressures may be used to determine the power required of the compressor.

Compression of the bubbles also capitalizes on the effect of surface tension that heat up the vapour to much higher temperature during bubble collapse like, for example, in cavitation phenomenon. Moreover, the specific volume of vapour in bubbles is considerably smaller, and thus, the same amount of cooling through evaporation can be achieved by an actuation unit with much lower pumping capacity than would be required in traditional compressor. The combination of these effects advantageously reduces power requirements for the present system in achieving an equivalent cooling load, which may otherwise have a higher power requirement when a conventional approach is used.

Additionally, an advantage of the present method over cold traps is that heat rejection is performed at temperatures higher than T_(env) and thus lesser energy is required.

Example 3: Further Components of the Present Method and Apparatus

It is important to note that due to large volume of the bubbles, the oil/water output have to be considerably larger than the oil input pipe. As the oil/water mixture that is withdrawn may contain large volume of bubbles, such oil/water/vapour mixture may have a low viscosity, large volume, and as a result, become destructive for the oil pump. The oil/water/vapour mixture may be a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid. Care, therefore, has to be taken in this regard. For example, oil can be first pumped out into a holding chamber where most of the bubbles are allowed to collapse. Accordingly, the present system or apparatus may further comprise a chamber configured to mix the mixture with a non-volatile non-polar liquid having substantially low polar fluid content to condense the vapour of the polar fluid.

As the flow progresses through the piping that is carrying the withdrawn oil/water mixture, it may be subjected to cooling using a heat exchanger. Due to high temperatures, dry cooling using finned metal pipe heat exchanger with air circulation mechanism can be effectively used. As cooling progresses, vapour bubbles tend to collapse and condense into liquid water. The overall volume of oil/water mixture is reduced, so it is practical to reduce heat exchanger piping either gradually or at certain locations.

While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced. 

1. A method of collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising: providing in an enclosed container an initial volume of the non-volatile non-polar liquid; maintaining a reduced pressure above the surface of the non-volatile non-polar liquid; introducing a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid; introducing a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid; and withdrawing an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid.
 2. The method according to claim 1, wherein the reduced pressure is set at a pressure which is sufficiently low to convert at least some of the polar fluid into the vapour of the polar fluid.
 3. The method according to claim 1, wherein introducing the second input stream comprises delivering the non-volatile non-polar liquid from a position which is at a same height as or above the first input stream.
 4. The method according to claim 1, wherein introducing the second input stream comprises delivering the non-volatile non-polar liquid with some polar fluid present in the non-volatile non-polar liquid.
 5. The method according to claim 1, further comprising mixing the mixture with a non-volatile non-polar liquid having substantially low polar fluid content to condense the vapour of the polar fluid.
 6. The method according to claim 1, further comprising cooling the mixture to condense the vapour of the polar fluid.
 7. The method according to claim 1, wherein the polar fluid comprises water.
 8. The method according to claim 1, wherein the non-volatile non-polar liquid comprises hydrocarbon, non-synthetic lubricant, mineral oil and/or vegetable oil.
 9. The method according to claim 1, wherein the vapour of the polar fluid comprises water vapour.
 10. An apparatus for collecting vapour of a polar fluid in a non-volatile non-polar liquid, comprising: an enclosed container comprising an initial volume of the non-volatile non-polar liquid; a first outlet connected to a pump which reduces pressure above the surface of the non-volatile non-polar liquid; a first inlet configured to introduce a first input stream comprising the polar fluid or a super-heated vapour of the polar fluid into the enclosed container, wherein the non-volatile non-polar liquid is less dense than the polar fluid and is disposed above the polar fluid; a second inlet configured to introduce a second input stream comprising the non-volatile non-polar liquid into a section of the enclosed container containing the non-volatile non-polar liquid; and a second outlet configured to withdraw an output stream from the section containing the non-volatile non-polar liquid, wherein the output stream comprises a mixture of the vapour of the polar fluid, the non-volatile non-polar liquid and optionally some of the polar fluid which has condensed from the vapour of the polar fluid.
 11. The apparatus according to claim 10, wherein the pump is a positive displacement pump.
 12. The apparatus according to claim 10, wherein the first inlet comprises one end disposed in the section containing the non-volatile non-polar liquid.
 13. The apparatus according to claim 10, wherein the second inlet comprises one end disposed at a position in the section containing the non-volatile non-polar liquid which is at a same height as or above the first inlet.
 14. The apparatus according to claim 10, wherein the second inlet is configured to introduce the second input stream comprising the non-volatile non-polar liquid with some polar fluid present in the non-volatile non-polar liquid.
 15. The apparatus according to claim 10, wherein the second outlet comprises one end disposed at a position in the section containing the non-volatile non-polar liquid which is at a same height as or above the first inlet.
 16. The apparatus according to claim 10, further comprising a chamber configured to mix the mixture with a non-volatile non-polar liquid having substantially low polar fluid content to condense the vapour of the polar fluid.
 17. The apparatus according to claim 10, further comprising a heat exchanger which cools the mixture to condense the vapour of the polar fluid. 